Problem: Christopher starts counting at 33, and he counts by fours. If 33 is the 1st number that Christopher counts. what is the 7th number that he counts?
Explanation: What is the first number that he counts? $33$ What is the second number that he counts? $\begin{align*}&33 + 4 \\ &= 37\end{align*}$ What is the third number that he counts? $\begin{align*}&33 + 4 + 4 \\ &= 33 + (2 \times 4) \\ &= 41\end{align*}$ What is the 7th number that he counts? $\begin{align*}&33 + (6\times4) \\ &= 33 + 24 \\ &= 57\end{align*}$